A Collaborative National Center for Fusion & Plasma Research

Michael C Zarnstorff

Deputy Director for Research

The Man Who Loves Science

Zarnstorff ponders how Lab can do more

By John Greenwald


Michael Zarnstorff couldn’t decide whether to major in physics, math or computer science. So he majored in all three at the University of Wisconsin-Madison, and co-owned a computer company on the side. “My normal rule of thumb is that I’m interested in almost everything,” said Zarnstorff, an award-winning physicist who joined the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) in 1984, and has been deputy director for research since 2009.

Zarnstorff’s broad curiosity dovetails with the task of supervising research that ranges from testing ideas for harnessing fusion to developing rockets for space flight.  His job encompasses keeping projects aligned with DOE goals and envisioning new research opportunities for PPPL, which is managed by Princeton University. “I always try to look at how we can do more,” he said.

Zarnstorff first showed an interest in science as a youngster in Madison. He recalled childhood kits called “Things of Science” that came in little blue boxes in the mail each month. His father was a University of Wisconsin professor who taught medical physics, a discipline that develops medical imaging devices, and ran a company that built insect traps that showed farmers how much spraying they needed to do. “I learned at a relatively early age how to use a lathe and other machine tools,” recalled Zarnstorff, who made parts for the traps with his younger brother, Dan, in the basement of their home, which their father and grandfather had built.

High school found Zarnstorff taking college courses as a senior and working in a University of Wisconsin physics laboratory. High school was also where he met his future wife, Sally, who went on to become a computer scientist. The couple’s son, Jonathan, is in middle school.

Zarnstorff and five classmates launched a hardware and software company while in college. They did consulting work for clients located as far away as the Netherlands and came close to landing a contract with Disney World in Florida. The partners named their company Shinar Digital after the plain where the Tower of Babel was situated, as described in the Bible’s book of Genesis. “Computers are to some extent a jumble of different languages,” said Zarnstorff. “We were willing to speak many of those languages, and we wanted to be a little bit funny too.” The company disbanded after Zarnstorff earned his doctorate and moved from Madison to PPPL.

Zarnstorff became a vegetarian during his undergraduate years.  “It was a health choice as much as anything,” he said, “and there’s also a little bit of choosing not to be cruel.” His brother is a vegetarian too. “Our parents are coping but they still find it mystifying,” said Zarnstorff. He has since gone his own way in footwear as well, wearing sandals for comfort year-round in New Jersey, where the winters are milder than in the Midwest.

Zarnstorff focused on plasma physics as a graduate student at Wisconsin, though it took him a while to make up his mind. High-energy physics, which uses accelerators to study sub-atomic particles, also intrigued him. But the promise of plasma as a fuel for clean-energy fusion carried the day. “It’s easy to find challenging problems in science,” Zarnstorff said. “But the challenges of plasma physics have an impact on society because of their connection to the energy supply.”

While working on those challenges, Zarnstorff co-discovered a key phenomenon called the “bootstrap current” that helps to control the plasma in experimental fusion devices called tokamaks. His co-discoverer was PPPL director Stewart Prager, who was Zarnstorff’s thesis adviser at Wisconsin at the time.  The two physicists received the American Physical Society’s 2008 Dawson Award for Excellence in Plasma Physics Research for their finding, which has helped to shape the design of a generation of tokamaks.

Zarnstorff confirmed the existence of the crucial current after joining PPPL. He and physicist James Strachan created high-pressure plasmas that revealed the current in the Laboratory’s Tokamak Fusion Test Reactor (TFTR), the world’s most powerful fusion facility in the 1980s and 1990s. The experiments found a sharp drop in the externally applied current inside the plasma as the pressure rose, a sure sign that the bootstrap current had emerged.

The process is like the production of current in barbecue-grill lighters, Zarnstorff said. Just as the crystal inside the lighters creates a current when squeezed, so the plasma gas inside a tokamak produces the bootstrap current when the pressure is raised.

Zarnstorff  went on to head several divisions of the TFTR project, which set records  for producing heat and fusion power before the device was decommissioned at the end of the 1990s. He then led the physics group for the National Compact Stellarator Experiment, an innovative facility whose construction was halted in 2008 when costs exceeded estimates. 

Zarnstorff became deputy director for research the following year. The promotion reunited him with Prager, who arrived from Wisconsin to head the Laboratory in 2009. The new leadership included Adam Cohen, who came from the Argonne National Laboratory outside Chicago to serve as deputy director for operations at PPPL.

Together with Prager and Cohen, Zarnstorff aims to broaden the scope of Laboratory research over the next five years while keeping it strongly engaged in efforts to harness fusion. Such efforts range from the current $94 million upgrade of the National Spherical Torus Experiment, the Laboratory’s largest project, to key design and technical support for ITER, a  $20-billion tokamak that is being built by the European Union, the United States and five other countries in the south of France. At the same time, “we are broadly engaged in applying research to developing new uses for plasma and understanding its role in the universe,” Zarnstorff said.

Recent initiatives that Zarnstorff has worked on include the rejuvenation of PPPL’s post-doctoral fellowship program, and the strengthening of the Laboratory’s collaborations with fusion experiments in Asia and Germany. Also under way is an increased focus on the development of liquid lithium to absorb the heat flux that strikes tokamaks’ inner, or plasma-facing, walls. “That’s clearly an area of potential strength for the Laboratory,” Zarnstorff said of the lithium work.

His own role is many-sided. “In essence, it’s to manage and help all the research activities within the Laboratory succeed,” he said. This calls not only for setting priorities, but for remaining open to new possibilities. “Planning and forethought are crucial,” said Zarnstorff, “but plans are made to be changed.”


  • Neoclassical and turbulent transport
  • Plasma confinement and stability in magnetic fields
  • Plasma transport barriers

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Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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